1. Field of the Invention
The present general inventive concept relates to an electrophotographic toner and a method of manufacturing the same.
2. Description of the Related Art
In an electrophotographic process or an electrostatic recording process, a developer used to visualize an electrostatic image or an electrostatic latent image can be classified into a two-component developer formed of toner and carrier particles and a one-component developer formed of only toner. The one-component developer can be classified into a magnetic one-component developer and a nonmagnetic one-component developer. Fluidizing agents such as colloidal silica are often added to the nonmagnetic one-component developer to increase a fluidity of the toner. Typically, toner includes coloring particles obtained by dispersing a colorant such as carbon black or other additives in a latex.
Methods of preparing toner include pulverization and polymerization. In the pulverization method, the toner is obtained by melting and mixing synthetic resins with colorants and, if required, other additives, pulverizing the mixture and sorting the particles until particles of a desired size are obtained. In the polymerization method, a polymerizable monomer composition is manufactured by uniformly dissolving or dispersing various additives, such as a colorant, a polymerization initiator and, if required, a cross-linking agent and an antistatic agent, in a polymerizable monomer. Then, the polymerizable monomer composition is dispersed in an aqueous dispersive medium, which includes a dispersion stabilizer, using an agitator to shape minute liquid droplet particles. Subsequently, the temperature of the mixture is increased and suspension polymerization is performed to obtain polymerized toner having coloring polymer particles of a desired size.
In an imaging device, such as an electrophotographic device or an electrostatic recording device, an image is formed by exposing an image on a uniformly charged image bearing unit to form an electrostatic latent image thereon, attaching toner to the electrostatic latent image to form a toner image, transferring the toner image onto a transfer medium such as transfer paper or the like, and then fixing the toner image to the transfer member by any of a variety of methods, including heating, pressurizing, solvent steaming and the like. In most fixing processes, the transfer medium with the toner image disposed thereon passes through fixing rollers and pressing rollers, and the toner image is fused to the transfer medium by heat and pressure.
Images formed by an imaging apparatus such as electrophotocopier should satisfy the requirements of high precision and accuracy. Conventionally, toner used in an imaging apparatus is usually obtained by using the pulverization method. In the pulverization method, color particles having a large range of particle size distribution are formed. Hence, in order to obtain satisfactory developing properties, there is a need to sort the coloring particles obtained through the pulverization method according to particle size so as to reduce a toner particle size distribution. However, it is difficult to precisely control the particle size and the particle size distribution by using a conventional mixing/pulverizing process in the manufacture of a toner which is suitable for an electrophotographic process or an electrostatic recording process. Also, when preparing a fine particle toner, the toner preparation yield is adversely affected by the sorting process. In addition, there are limits to the change/adjustment of a toner design in order to obtain desirable charging and fixing properties. Accordingly, polymerized toner, the size of toner particles of which is easy to control and which does not need to undergo a complex manufacturing process such as sorting, has been highlighted recently.
When toner is prepared through the polymerization method, polymerized toner having a desired toner particle size and toner particle size distribution can be obtained without pulverizing or sorting.
However, even with polymerized toner, the toner still needs to have functional physical properties such as fixability and durability in order to obtain excellent printing performance and high image quality when printing. To develop such toners, thixotropy needs to be optimized.